feat(editor): add constrain module

editor/src/lang/constrain.rs

@@ -0,0 +1,32 @@
+use crate::lang::pool::{Pool, PoolVec};
+use crate::lang::{ast::Expr2, expr::Env, types::Type2};
+
+use roc_can::expected::Expected;
+use roc_module::symbol::Symbol;
+use roc_region::all::Region;
+use roc_types::types::Category;
+
+#[derive(Debug)]
+pub enum Constraint {
+    Eq(Type2, Expected<Type2>, Category, Region),
+    // Store(Type, Variable, &'static str, u32),
+    // Lookup(Symbol, Expected<Type>, Region),
+    // Pattern(Region, PatternCategory, Type, PExpected<Type>),
+    True, // Used for things that always unify, e.g. blanks and runtime errors
+          // SaveTheEnvironment,
+          // Let(Box<LetConstraint>),
+          // And(Vec<Constraint>),
+}
+
+pub fn constrain_expr(env: &mut Env, expr: &Expr2, expected: Expected<Type2>) -> Constraint {
+    use Constraint::*;
+
+    match expr {
+        Expr2::Str(_) => Eq(str_type(env.pool), expected, Category::Str, Region::zero()),
+        _ => todo!("implement constaints for {:?}", expr),
+    }
+}
+
+fn str_type(pool: &mut Pool) -> Type2 {
+    Type2::Apply(Symbol::STR_STR, PoolVec::empty(pool))
+}

editor/src/lang/mod.rs

@@ -1,4 +1,5 @@
 pub mod ast;
+pub mod constrain;
 mod def;
 pub mod expr;
 mod module;
@@ -6,4 +7,4 @@ mod pattern;
 pub mod pool;
 pub mod roc_file;
 pub mod scope;
-mod types;
+pub mod types;